پاسخ گندم رقم بم به اثرات متقابل شوری آب آبیاری و سطوح مختلف کود سولفات پتاسیم

چگونگی تاثیر تنش شوری بر نیاز غذایی گیاهان یکی از چالش‌های تغذیه گیاهی می باشد. در برخی از منابع، مصرف بیشتر کودهای شیمیایی از جمله کودهای نیتروژنی، فسفری و پتاسیمی در شرایط شور نسبت به شرایط غیر شور توصیه شده است. اما، در برخی دیگر از منابع، مصرف کمتر و یا مصرف یکسان کود در شرایط شور و غیر شور پیشنهاد شده‌است. پژوهش اخیر در راستای بررسی نیاز کودی گندم (رقم بم) در شرایط مختلف شوری آب آبیاری در مزرعه تحقیقاتی مرکز ملی تحقیقات شوری واقع در یزد اجرا شد. این تحقیق دارای سه سطح شوری آب آبیاری 1.88، 7.22 و 14.16 دسی زیمنس بر متر و چهار سطح کود سولفات پتاسیم شامل صفر، 100، 200 و 300 کیلوگرم در هکتار بود. آزمایش در قالب طرح آماری بلوک های کامل تصادفی به صورت اسپلیت پلات با سه تکرار اجرا شد. نتایج نشان داد که با افزایش شوری آب آبیاری از 1.88 به 7.22 دسی زیمنس بر متر، عملکرد دانه و کاه گندم کاهش معنی داری نداشت. با افزایش شوری آب آبیاری به 14.16 دسی زیمنس بر متر، عملکرد دانه و کاه حدود 50 درصد کاهش یافت. بررسی اثرات متقابل شوری و کود سولفات پتاسیم نشان داد که مصرف کود سولفات پتاسیم تاثیر معنی داری بر عملکرد دانه و کاه گندم در هیچیک از سطوح شوری مورد مطالعه نداشت. بنابراین، فرضیه افزایش تحمل به شوری گندم با مصرف کود پتاسه در شرایط مزرعه ای این تحقیق مردود شد. به طور کلی، برای تولید حدود 6 تن دانه و 9 تن کاه گندم در شرایط گرم و خشک استان یزد و در خاک آهکی با پتاسیم قابل جذب معادل 150 میلی گرم در کیلوگرم خاک که با آب با هدایت الکتریکی 1.88 تا 14.16 دسی زیمنس بر متر آبیاری شود مصرف کود سولفات پتاسیم ضرورتی ندارد.

Wheat (Bam variety) responses to interactive effects of irrigation water salinity and different rates of potassium sulphate fertilizer

IntroductionSalinity stress is known as a worldwide abiotic stress responsible for reduced crop production. It is estimated that annual losses of yield due to salt induced land degradation is US$ 27.3 billion globally (Qadir et al., 2014). Social and economic dimentions of salinity stress can be employment losses as well as environmental degradation (Butcher et al., 2016). In addition, it is well documented that application of chemical fertilizers usually improve plant performance under saline conditons but results in plant fertilizer requirement under salt affected soils are contrary. While there is little evidence of yield benefits due to application of fertilizers in salinized fields at rates beyond optimal in nonsaline conditions, there is enough evidence indicating that soil salinity does not affect or decrease plant fertilizer needs (Hanson, 2006). A hypothesis that potassium (K) application can reduce the negative effects of salinity on plant performance has been proposed, but, contradictory results have been reported. These include a reduction in salinity damage to crops when high concentrations of K are present in growth media as well as no response to K fertilizer under salinity or even a negative effect of K addition on salt tolerance (BarTal et al., 1991). These contradictory results can be attributed to the types of experiments (field, greenhouse or laboratory), composition of the saline substrate, studies conducted over the short term vs. the long term and many other differences in experimental conditions (Grattan and Grieve, 1999).Thus K fertilizer management may need to be modified under arid and semiarid conditions of Yazd peovince with wide range of irrigation water qualities. Accordingly, the objectives of this field study were to (a) elucidate the interactions between K nutrition and the salinity of irrigation water and their effects on wheat growth and (b) test the possibility of wheat improvement at saline conditions by applying higher levels of K fertilizer. Materials and methodsA field experiment was conducted on wheat at Sadooq Salinity Research Station, Ashkezar, Yazd, Iran. The soil at the experimental site was calcareous with 30.92% total nutrient value, sandy loam texture, pH 8.06 and 0.22 % organic carbon. Mean annual temperatue is 18°C and precipitation is 70 mm. The treatments, four potassium sulphate application rates (0, 100, 200 and 300 kg ha1) and three irrigation water qualities (1.88, 7.22 , 14.16 dS/m), arranged in a randomized block, split plot design with three repelications. Consisting 12 rows of wheat, each field plot was 3*5 m. All plots received common agricultural practices including tillage and fertilizer application. Rgarding typical recommendations and guidelines for this region and soil type (Balali et al., 2000: Moshiri et al., 2015), all fertilizers, except urea that applied in 4 splits, were soilapplied before plnating and included 100 kg ha1 triple superphosphate, 40 kg ha1 FeSO4, 40 kg ha1 ZnSO4, 40 kg ha1 MnSO4 and 20 kg ha1 CuSO4. To model the relationship between plant properties and irrigation water salinity, the data were subjected to different regression models at the probability level of 0.01 and 0.05 with the help of the Sigmaplot software. The analysis of variance for different parameters was done following ANOVA technique. When F was significant at p ≤ 0.05 level, treatment means were separated using DMRT. Results and discussionThe results showed that increasing irrigation water salinity to 7.22 dS/m did not significantly affect wheat graine yield. This is due to the nonsignificant effect of salinity on 1000 seed weight, harvesting index and non bearing spikelets in addition to the significant increase in spike length, bearing spikelets, bearing spikelet numbers, seed number per spikes and total spikelet numbers. At the same time, the results showed 50% decrease in wheat grain and straw yield due to the increase in the salinity of irrigation water from 1.88 to 14.16 dS/m. As application of K fertilizer did not affect wheat performance significantly, it was concluded that K application did not increase wheat tolerance to salinity stress under field conditions of our experiment. ConclusionOverall, it was concluded that K fertilizer was not necessary for wheat production (6 Mg ha1 grain and 9 Mg ha1 straw) under saline and nonsaline calcareous soils of Yazd province with soil available K of 150 mg kg1. Key words: Calcareous soils, Irrigation Water and Yazd.