Using a chlorophyll meter to manage nitrogen applications to corn with high nitrate irrigation water

Abstract

Chlorophyll meters can aid in measuring the nitrogen (N) status of corn (Zea mays), but will the use of chlorophyll meters decrease total N use or increase corn grain yield? Use of a fully fertilized reference strip with a chlorophyll meter (SPAD 502) is an accepted management strategy. The critical level of relative chlorophyll necessary to trigger supplement N is uncertain. To determine the impact of using a 96 or 92% critical level of chlorophyll readings relative to a fully fertilized reference strip, 0 and 112 N kg ha^‐1 were applied at planting for three years. Specific plots were fertilized with an additional 56 kg N ha^‐1 whenever the meter reading on those plots was below either 96 or 92% of the reference area. The experiment was conducted on two Typic Haplustolls and an Entic Haplustoll. Irrigation water contained nitrate ranging from 20 to 38 mg L^‐1. Irrigation water supplied from 43 to 120 kg N ha^‐1 season^‐1. For all treatments that received N‐supplements based on the chlorophyll meter, yields were statistically the same. The chlorophyll meter is a useful management tool to help schedule N applications, when irrigation water is contaminated with nitrate since use of the chlorophyll meter prevented any yield limiting N deficiencies.     

Use of a chlorophyll meter to evaluate the nitrogen status of dryland winter wheat

Abstract

Chlorophyll meter leaf readings were compared to grain yield, leaf N concentration and soil NH₄‐N plus NO₃‐N levels from N rate studies for dryland winter wheat Soil N tests and wheat leaf N concentrations have been taken in the spring at the late tillering stage (Feekes 5) to document a crop N deficiency and to make fertilizer N recommendations. The chlorophyll meter offers another possible technique to estimate crop N status and determine the need for additional N fertilizer. Results with the chlorophyll meter indicate a positive association between chlorophyll meter readings and grain yield, leaf N concentration and soil NH₄‐N plus NO₃‐N. Additional tests are needed to evaluate other factors such as differences among locations, cultivars, soil moisture and profile N status.     

Determination of cotton nitrogen status with a handheld chlorophyll meter

The ability of a hand‐held chlorophyll meter (SPAD‐502 Chlorophyll Meter³, Minolta Camera Co., Ltd., Japan) to determine the N status of cotton (Gossypium hirsutum L.) was studied at field sites in Alabama and Missouri. Meter readings on the uppermost fully‐expanded leaf were compared to leaf‐blade N and petiole NO₃‐N at first square, first bloom and midbloom as to their seed cotton yield predictive capability. Nitrogen was applied at rates of 0, 45, 90, 135, 180 and 225 kg ha^‐1 to establish a range of cotton chlorophyll levels, tissue N concentrations, and seed cotton yields. A typical curvilinear cotton yield response to N fertilizer was observed in Alabama experiments.

Because of adverse weather conditions, cotton yield in Missouri experiments did not respond to N. Chlorophyll meter readings were significantly correlated to leaf‐blade N concentration at all three stages of growth for all experiments. In Alabama, chlorophyll meter readings compared favorably to leaf‐blade N and petiole NO₃‐N with respect to their seed cotton yield predictive capability at all three stages of growth. It appears that hand‐held chlorophyll meters would be as reliable as leaf‐blade N and petiole NO₃‐N for predicting supplemental N fertilization requirements of cotton. However, more research will be required prior to use of chlorophyll meter readings for routine cotton‐N recommendation purposes.     

Chlorophyll meter as nitrogen management tool in malting barley

Abstract

Variable precipitation in many regions makes it difficult to predict yield goals and nitrogen (N) rates for malting grade barley (Hordeum vulgare L.). During years with below normal growing season precipitation, barley fertilized at the recommended rate often exhibits grain protein concentrations exceeding what is acceptable for malting. A study was conducted to evaluate the chlorophyll meter as a N management tool. Barley was grown under several N rates in the field. Chlorophyll meter readings and N additions were made at the Haun 4 to 5 growth stage, and grain yield and protein concentrations were evaluated at maturity. Chlorophyll meter readings, normalized as meter reading from treatment plot divided by that from a plot receiving a full N treatment at the Haun 4 to 5 growth stage, were correlated with grain yield (r²=0.67). Stands having normalized chlorophyll meter readings below 95% responded to N additions with yields equivalent to the fully fertilized stand and grain protein concentrations acceptable for malting. A N management strategy is proposed whereby 40 to 50% of the N calculated for the yield goal is applied at planting and a fully fertilized reference strip is included for each variety or soil type. At the Haun 4 to 5 growth stage, chlorophyll meter readings are taken in the reference strip and in the field. Normalized chlorophyll meter readings below 95% of the reference strip indicate a need for additional N fertilizer. This strategy will provide producers with additional time (up to a month) to evaluate growing season conditions before investing in additional crop inputs and will improve the likelihood that a barley crop acceptable for malting will be produced.     

Evaluation of the Minolta SPAD‐502 chlorophyll meter for nitrogen management in corn

The field study investigated the relationship of Minolta SPAD 502 (SPAD) readings to applied nitrogen (N) fertilizer rate, corn (Zea mays L.) yield, and leaf N concentration. The experiment was conducted on a total of six sites in Illinois during 1991 and 1992. Ten different open pedigree corn hybrids were grown at a final population of 65,000 plants ha^‐1. Nitrogen was applied at four rates(0, 90, 180, and 270 kgN ha^‐1) as 28% liquid N solution. Significant main effects of environment (E), and hybrid (H), and E x H interaction were detected for all measured parameters. SPAD readings and leaf N concentration at all sampling times (V7, R1, and R4) as well as grain N concentration were affected by N fertilizer rate. Maximum mean grain yield and maximum grain N concentration were obtained at 110 and 195 kg N ha^‐1, respectively. At all sampling times the correlation of SPAD readings to N fertilizer rate were low but significant (R=0.22 at V7 and R1, R=0.11 at R4). SPAD correlation to corresponding leaf N concentration improved over time. The Pearson correlation was R=0.33 at V7 and increased to R=0.78 at R4. The SPAD meter did a good job at providing a measure of the relative greenness of living leaves at a specific point in time. Chlorophyll readings can therefore be useful in detecting N deficiencies in growing crops. But, the SPAD meter cannot be used to make accurate predictions of how much fertilizer N will be needed by a crop during the future growing season. We conclude then that the SPAD meter will be most useful as a diagnostic aid rather than a tool for N management in corn.     

Using a chlorophyll meter to predict nitrogen fertilizer needs of winter wheat

Abstract

Although it has been shown that the nitrogen (N) concentration of winter wheat (Triticum aestivum L. em Thell) at Feeke's growth stage 5 (GS 5) can be used to assist in making more accurate spring N fertilizer recommendations, the need remains to find a more convenient and accurate means for predicting N fertilizer needs of wheat. We conducted seven N fertilizer response experiments over two years in central and southeastern Pennsylvania to determine if chlorophyll meter readings of wheat leaves at GS 5 could predict whether a significant, positive grain yield response to N fertilizer would be obtained. The chlorophyll meter readings at GS 5 were more accurate (correctly predicting response to N fertilizer in 24 of 25 treatments for a 4% error rate) than GS 5 plant N concentration (20% error rate). There were too few treatments with a positive response to N fertilizer to be able to determine if chlorophyll meter readings could be used to accurately predict N fertilizer rates needed for economic optimum yield.     

Use of a hand‐held chlorophyll meter in winter wheat: Evaluation of different measuring positions on the leaves

A portable chlorophyll meter (Minolta SPAD‐502) was used to assess the nitrogen status of winter wheat (Triticum aestivum L.) in two fertilizer trials at Apelsvoll Research Centre, located in south‐east Norway. The midpoint of the last fully developed leaf was found to be the best position on the winter wheat plant on which to take chlorophyll meter readings. This conclusion was reached after examination of the relationships between soil‐plant analyses development (SPAD) readings taken at different positions on the plant and leaf nitrogen concentration, grain yield and grain protein content. Emphasis was also laid on finding a measuring position that was convenient from a practical point of view. The relationships between chlorophyll meter readings and the parameters investigated were better at Zadoks growth stage (GS) 49 than earlier in the season at GS 31.     

主动遥感光谱仪Greenseeker与SPAD对玉米氮素营养诊断的研究

以手持式主动遥感光谱仪Greenseeker和叶绿素仪SPAD对玉米不同氮素水平下各个生育期的NDVI值及叶片SPAD值进行测试,研究不同氮素对玉米群体和个体营养状况的变化以及田间条件下简便、快速、非接触性的作物氮素营养状况诊断方法。结果表明,在一定的范围内随着氮肥用量的增加NDVI值也增加,氮肥施用量为N 300kg/hm2时NDVI值达到最高,NDVI 与氮肥施用量符合线性加平台的关系;玉米不同生育期间NDVI 值变化明显,苗期NDVI值比较低,大喇叭口期NDVI 值达到最高,以后逐渐下降并在抽雄期后趋于稳定。SPAD值与NDVI 值的变化趋势相一致,SPAD值与叶绿素含量成正相关关系,大喇叭口期完全展叶的SPAD 与产量存在正相关关系。手持式主动遥感光谱仪Greenseeker和叶绿素仪SPAD结合能够对玉米的氮素营养状况作营养诊断。     

Fertilizer Bands Affect Early Growth of Corn

Nitrogen (N) applied in bands across cornfields often induces differences in plant height, leaf color, and growth stage of corn (Zea mays L.). Especially during wet springs, plants growing immediately over the bands are often noticeably taller and greener for a short period. Plants growing between the bands experience N deficiency until their roots reach the bands. The impacts of such short periods of N deficiency on plant early growth have received little attention. We studied the effects of tracks left by fertilizer applicator on corn growth stage, plant height, and leaf chlorophyll meter readings (CMRs) in a field where conditions seemed favorable for a fertilizer-induced advancement in growth stage. Measurements showed that the reduced plant height or leaf color attributable to a temporary N deficiency was mainly associated with the delay of growth stages and might have little influence on final grain yield.     

Chlorophyll meter predicts nitrogen status of tall fescue

The nitrogen (N) status of a crop can be used to predict yield and supplemental N fertilizer requirements, and rapid techniques for evaluating the N status of crops are needed. A study was conducted to determine the feasibility of using a hand held chlorophyll meter (SPAD 502, Minolta Co. Ltd., Japan) to monitor N status of tall fescue (Festuca arundinacea Schreb.). Four diverse tall fescue genotypes were grown at three locations in Alabama and fertilized at four N‐rates from 0 to 336 kg ha^‐1. A similar experiment was conducted in the greenhouse using soil from the same field sites. Chlorophyll meter readings (SPAD) were taken, and extractable chlorophyll content, tissue N concentration and dry matter yield were determined at harvest. SPAD, extractable chlorophyll content, tissue N concentration, and dry matter yield increased quadratically (0.67 < R² < 0.99) with increasing N fertilization in both experiments. All genotypes responded similarly to applied N, with some differences in magnitude. Relationships between SPAD meter readings and extractable chlorophyll and tissue N concentrations were linear with r² > 0.95. An additional independent variable, the square root of the inverse of SPAD, lowered the residual mean square by 11 and 16%, respectively, for tissue‐N and chlorophyll concentrations, but did not increase the R². This would be preferred for predictive purposes. Tissue N concentrations at higher N‐rates were sufficient for maximum yield which occurred at 290 and 248 kg N ha^‐1 for greenhouse and field, respectively, but were lower than previously reported sufficiency values. The chlorophyll meter is an easy and efficient method of detecting tall fescue N status.     

行距配置方式对夏玉米氮素吸收利用及产量的影响

为确定黄淮南部夏玉米产区机械化生产适宜的行距配置方式,2012—2013年同时在河南省方城县和辉县两个试验点设置大田试验,以高、中、低3种株高类型的玉米杂交种‘先玉335’、‘郑单958’和‘512-4’为材料,设置2个种植密度(低:60 000株·hm~(-2);高:75 000株·hm~(-2))、5个行距配置方式(50 cm、60 cm、70 cm、80cm等行距和80 cm+40 cm宽窄行距),研究了不同株型玉米品种在不同密度和行距配置条件下对氮素吸收利用效率和产量的影响。结果显示,低密度种植条件下,高秆的‘XY335’和矮秆的‘512-4’均以60 cm等行距处理产量优势明显;中秆的‘ZD958’在辉县和方城分别以60 cm和70 cm等行距产量最高。在高密度种植条件下,高秆的‘XY335’和中秆的‘ZD958’均以60 cm等行距处理产量最高;而矮秆的‘512-4’则以50 cm等行距种植产量优势明显,但与60 cm等行距处理差异不显著。植株氮积累量随行距的扩大呈先升高后降低的趋势,以60 cm等行距的氮积累量较大,低密度时显著高于80 cm等行距和80 cm+40 cm宽窄行距处理,而高密度下与各行距处理差异不显著;不同品种植株氮积累量对行距反应不同,高秆品种在行距间差异不显著,中秆品种80 cm等行距最低且与其余行距处理差异显著,矮秆品种50 cm和60 cm等行距氮积累量最高且与其余行距差异显著。两个密度种植条件下,籽粒氮积累量和氮素收获指数均随行距的扩大先升高后降低,在60 cm等行距处理达到最大值,并且均显著高于其他行距处理;氮肥偏生产力随行距的扩大呈现先升高后降低的趋势,60 cm等行距处理较高,但在低密度下与其他行距处理差异不显著,高密度时与80 cm等行距处理差异显著。与其他行距处理相比,60 cm等行距处理具有相对较高的氮素吸收利用效率和产量,能够较好地协调玉米土壤与植株的氮素吸收利用关系,兼顾不同株高类型玉米品种在一定密度范围内获得高产,可作为目前黄淮南部地区夏玉米统一的行距配置方式进行推广。     

不同气候和土壤条件下玉米叶片叶绿素相对含量对土壤氮素供应和玉米产量的预测

叶绿素仪可以用于估测作物和土壤氮素供应状况,本研究通过野外土壤置换试验评估叶绿素仪在不同区域的适用性。在黑龙江海伦（中温带）、河南封丘（暖温带）和江西鹰潭（中亚热带）设置3种主要农田土壤（黑土、潮土、红壤）的异地置换对比试验,研究了不同气候和土壤条件下玉米叶绿素相对含量对土壤氮素供应的响应及其对玉米产量的预测性。研究结果表明:不同气候和土壤条件下,玉米生长旺盛期功能叶的叶绿素相对含量（叶绿素仪SPAD值）和土壤表层（0—20 cm）硝态氮、无机氮含量相关性显著,说明叶绿素仪测定值可以在玉米生长旺盛期反应土壤氮素供应情况;玉米生长旺盛期功能叶叶绿素相对含量和土壤表层硝态氮含量均与玉米子粒产量呈显著相关,说明叶绿素仪可以在玉米生长旺盛期估测玉米子粒产量,且不受地域、土壤类型的影响。     

叶绿素仪在夏玉米氮营养诊断中的应用

叶绿素仪(SPAD-502)的出现使通过无损伤的田间速测对作物进行氮营养诊断成为可能。采用简单的试验和研究方法在田间条件下研究了叶绿素仪应用于夏玉米氮营养诊断的可行性。研究结果表明,应用叶绿素仪监测夏玉米氮营养状况的最佳测定部位为最上部完全展开叶的中部,该部位叶绿素仪测定值与作物全氮、施氮量及产量之间均有较好的相关性。由于作物品种对叶绿素测定影响很大,需要通过相对叶绿素仪读数的方法对其进行校正,校正后叶绿素仪对夏玉米追肥推荐中营养状况的预测精度为66.7%。     

Plant density,distribution, and fertilizer effects on yield and quality of irrigated corn silage

Abstract

Grain deficits frequently occur in the Southeastern Atlantic Coastal Plain because erratic rainfall patterns and soil properties often limit corn (Zea mays L.) yields, however, harvesting corn for silage may enable farmers to produce a second grain crop during the same calendar year. Effects of row spacing, plant population, and fertilizer program on yield, quality, and mineral concentrations of corn silage grown with irrigation on Typic Paleudult soils were therefore investigated. Two plant population treatments which averaged 7.0 and 10.1 plants m^‐2 were evaluated with two fertilizer programs that differed in N, N and K, and N, P, and K in 1980, 1981, and 1982, respectively. Each plant density by fertilizer combination was evaluated in single rows spaced 96 cm apart and in twin rows which approximately doubled the intrarow plant spacing. Plot size for the 2×2×2 factorial experiment ranged from 30 to 44 m². Yield, quality, and mineral concentrations of corn silage grown in single rows spaced 96 or 75 cm apart and twin rows were also evaluated in large (185 m²) plots under center pivot irrigation during 1981 and 1982.

Dry matter yields of 22 to 26 Mg ha^‐1 were achieved with plant densities of 6.7 to 13.5 plants m^‐2 at both experimental sites. Highest silage yields were produced with stand densities of 9 m or more planted in single 75 cm or twin rows, but yield differences were statistically significant at P(0.05) in only two of five site years. Increasing total N‐P‐K application beyond 200–30–167 kg ha”; increased crude protein slightly in 1980 and significantly in 1981 and 1982. Concentrations of Mn and Zn in silage were increased by higher fertilization, presumably because nitrification reduced surface soil pH and increased their availability. Dry matter yield, fiber, energy, and other mineral nutrients were not significantly influenced by fertilizer program. These experiments identified management practices for the Atlantic Coastal Plain which resulted in corn silage yields equal to those produced in the cooler mountain region of Georgia and that exceeded current average production in South Carolina by approximately 40% without reducing apparent feed quality.     

Leaf and canopy optical characteristics as crop‐N‐status indicators for field nitrogen management in corn

The primary constraint of predicting the economic optimum nitrogen rate (EONR) for corn (Zea mays L.) is the high variability of soil nitrogen (N) supply due to environments, soil types, manure, and cropping histories. Portable instruments have been developed to measure leaf and canopy optical characteristics for determining plant N status. The objectives of this field study were to: (1) evaluate leaf and canopy optical properties including transmittance, reflectance, and fluorescence as indicators of corn N status with soil types, developmental stages, and N‐application rates, (2) compare the efficiency of two commercial radiometers that are designed to measure canopy reflectance, and (3) assess the constraints of these crop‐based indicators as a possible guide for real‐time N sidedressing in corn. Field experiments with different levels of N, soil types, and corn hybrids were conducted at three sites in Ottawa, ON, Canada, in 2004 and 2005. Leaf chlorophyll concentrations (SPAD chlorophyll meter), chlorophyll fluorescence (OS‐30), leaf area, and canopy reflectance (NDVI measured by CropScan and GreenSeeker radiometers) were simultaneously measured at several growth stages, while grain yield was determined at harvest. Our results show that canopy reflectance (NDVI) displayed similar efficiency as an indicator of N status on both soil types and corn hybrids in the two consecutive years. The chlorophyll readings often differentiated N‐deficient from N‐sufficient plots and therefore were a promising indicator for predicting corn N requirements. The fluorometer device evaluated in this study was unable to characterize corn N status.     

Ammonium concentration in solution affects chlorophyll meter readings in tomato leaves

Abstract

Combinations of NH₄‐N:NO₃‐N usually result in higher tomato (Lycopersicon esculentum Mill.) yields than when either form of nitrogen (N) was used alone. Leaf chlorophyll content is closely related to leaf N content, but the effect of the NH₄‐N:NO₃‐N ratio on leaf greenness was not clear. The objective of this study was to determine the influence of NH₄‐N:NO₃‐N ratios on chlorophyll meter (SPAD) readings, and evaluate the meter as a N status estimator and tomato yield predictor in greenhouse production systems. Fruit yield and SPAD readings increased as the amount of NH₄‐N in solution increased up to 25%, while higher ratios of NH₄‐N resulted in a decline in both. The N concentration in tomato leaves increased as concentration of NH₄‐N in solution increased. Fruit yield increased as chlorophyll readings increased. SPAD readings, total N in leaves, fresh weight of shoots, and fruit yield all showed a quadratic response to NH₄‐N, reaching a peak at 25 or 50% of N as NH₄‐N. SPAD readings taken at the vegetative and flowering stages of growth had the highest correlation (r²=0.54) with N concentration in leaves, but this could not be used as a reliable estimate of N status and fruit yield. Lack of correspondence between high N concentration values and fruit yield indicated a detrimental effect of NH₄‐N on chlorophyll molecules or chloroplast structure. The SPAD readings, however, may be used to determine the optimum NH₄‐N concentration in solution to maximize fruit yield.     

Photosynthesis,Chlorophylls, and SPAD Readings in Coffee Leaves in Relation to Nitrogen Supply

The export of nitrogen (N) from senescent plant parts is important for the efficient use of this macronutrient. The objective of this study was to establish correlations among the photosynthetic pigment content, total N, and the photosynthetic variables with the SPAD‐502 readings in Coffea arabica leaves. Correlations were established among the chlorophyll content, N content, and chlorophyll a and b with SPAD‐502 readings taken on coffee leaves at different months. The results show that all variables decreased with time. However, correlation increased linearly with N doses. Total chlorophyll presented a direct linear correlation with readings of the portable chlorophyll meter. The SPAD readings have shown to be a good tool to diagnose the integrity of the photosynthetic system in coffee leaves. Thus, the portable chlorophyll SPAD‐502 instrument can be used to evaluate the N status and can also help to evaluate the photosynthetic process in coffee plants.     

Tomato leaf chlorophyll meter readings as affected by variety,nitrogen form,and nighttime nutrient solution strength

Leaf chlorophyll content is closely related to leaf nitrogen (N) content, so it is reasonable to assume that ammonium‐N (NH₄‐N): nitrate‐N (NO₃‐N) ratio in the nutrient solution used to grow tomatoes (Lycopersicon esculentum Mill.) hydroponically may affect leaf greenness, and consequently chlorophyll meter (SPAD) readings. It has also been shown that increasing nutrient solution strength (NSS) increases tomato productivity, but there are no reports regarding how NSS affects SPAD readings under greenhouse conditions. Genotype may also influence SPAD readings, and standardization for cultivar and sampling time may be needed. The objective of this study was to characterize SPAD readings for five tomato cultivars and SPAD reading response to a combination of two NSS (1X and 4X Steiner solution strength daily applied 18 days after transplanting at 7 p.m.) and two concentrations of NH₄‐N in solution (0 and 25%) in order to evaluate the potential of SPAD readings as a tomato yield predictor in greenhouse production systems. The SPAD readings were not uniform across tomato varieties tested, being consistently higher for ‘Max’ and lower for the other varieties. Initially, SPAD readings for tomato varieties used in this study were low at the vegetative stage, and increased up to 40 DAT, but subsequently decreased at 49 DAT, or the fruit set of the first and second clusters. After this time, SPAD readings showed no variation. Chlorophyll meter readings for ‘Max’ were higher in the top plant layers, but decreased in the top plant layer of the other tomato varieties. The SPAD readings were higher for plants supplied with 25% NH₄‐N than those without NH₄‐N in solution, but the use of a nighttime nutrient solution did not affect SPAD readings. None of the possible interactions among tomato variety, NH₄‐N: NO₃‐N ratio, and NSS were consistently significant.     

叶绿素仪在氮肥推荐中的应用研究进展

叶绿素仪(Chlorophyll.meter)是近年来欧美一些国家在推荐施氮中开始使用的一种新型便携式仪器。这种仪器以叶绿素对红光和近红外光的不同吸收特性为原理来测定植物叶片的相对叶绿素含量,通过叶绿素与叶片全氮的关系来反映作物的氮营养状况,进而确定作物是否缺氮。这种新型仪器的使用为简便、快速、准确地进行氮肥推荐提供了一种新的思路。因此,通过研究不同作物,不同种植条件下叶绿素仪测定值与作物叶片全氮、作物产量之间的相关性,确定叶绿素仪测定值的临界水平,以及不同作物的测定部位、样品采集数量及影响测定准确性的因素,使这种技术尽快地应用于田间生产,有助于推动我国推荐施氮技术的进步。     

Influence of nitrogen rates and row spacing on corn yield,protein content,and other plant parameters

New maize hybrids has been intensively used as the first and second crop at the Cukurova region of Turkey in recent years. Therefore, nutritional problems of corn needs to be solved for the optimum yield, and protection from the potential insect and disease damages. Influence of nitrogen (N) and row spacing (RS) on corn yield, grain protein content, and selected plant parameters have been studied under field conditions in 1994 and 1995. Nitrogen was applied in the rates of 200, 250, 300, and 350 kg N ha^‐1 to main plots where row spacings were 10, 15, 20, and 25 cm in each subplots. Phosphorus (P) and potassium (K) were applied to each plot as basal rates. The experiment was arranged in a split‐plot design in three replications. During course of the experiment and after harvest, selected plant parameters, leaf nutrient contents, root length, grain yield, and crude protein content were measured, and the data were statistically analyzed for determination of treatment effects. The selected plant parameters either influenced by N, RS, or both in 1994 and 1995. The leaf N content was affected by N and RS in 1995, and a RS effect was only observed in 1994. Grain yield was influenced by RS and N and RS in the first and second years, respectively. Grain yield ranged between 7.3 to 12.8 Mg ha"¹ for both years. Treat ment effects on crude protein content was significant in 1994 but no response was obtained in 1995.