等氮配施有机肥对喀斯特峰丛洼地农田作物产量与养分平衡的影响

基于自2006年在广西喀斯特峰丛洼地区开展的长期玉米/大豆套作定位施肥试验,选择2010—2014年监测数据,探讨等氮量投入条件下,不同比例有机肥替代无机氮肥对喀斯特峰丛洼地玉米/大豆套作系统作物产量及土壤养分的影响,为喀斯特峰丛洼地农田作物高效施肥及提高土壤肥力提供理论依据。试验选取4个处理:对照(不施肥,CK)、平衡施用化肥(NPK)、有机粪肥替代30%化肥氮(C7M3,按氮素计算,不足30%的PK用无机肥补充,肥料总量与NPK处理相同,有机粪肥为牛粪,下同)、有机粪肥替代60%化肥氮(C4M6,按氮素计算,不足60%的PK用无机肥补充),每个处理4次重复。于2010年、2012年、2014年大豆收获后采集土壤样品,测定土壤养分状况。结果表明:1)施肥处理土壤有机质、全氮、速效磷及速效钾含量均高于CK处理,其中C4M6处理有机质含量显著高于NPK处理(P0.05),全氮、速效磷和速效钾含量随着有机粪肥施用量的增加而增加。2)长期不同施肥处理玉米和大豆产量分别是不施肥处理的4.15~4.36倍、2.47~2.58倍。不同施肥处理的增产效果为C4M6NPKC7M3,但施肥处理间差异不显著(P0.05)。3)长期不施肥CK处理玉米产量随着试验年限推移呈下降趋势,降幅为5.45 g·m~(-2)·a~(-1),大豆产量却表现出增加趋势,增幅为1.50 g·m~(-2)·a~(-1)。长期施肥处理中,玉米和大豆产量总体呈增加趋势。4)施肥处理中,玉米季表现为钾素亏缺(NPK处理除外),大豆季表现为氮素亏缺。综合两季作物,只有C4M6钾素表现亏缺,亏缺量为7.9 kg·hm~(-2)。磷素在各施肥处理中盈余量较大,分别为81.2 kg·hm~(-2)(NPK)、83.4 kg·hm~(-2)(C7M3)和74.8 kg·hm~(-2)(C4M6)。综上,在喀斯特峰丛洼地玉米/大豆套作制度下,基于作物产量及土壤养分表观平衡特征提出有机粪肥可以代替部分化肥施用,在玉米季适当"减氮、稳磷和增钾",大豆季"稳氮、减磷和减钾"的施肥措施。

Effect of partial replacement of inorganic N with organic manure on crop yield and soil nutrient balance in arable ecosystem in karst peak-cluster depression

Based on a long-term experiment on maize-soybean relay intercropping system in the karst peak-cluster depression in Guangxi, the effects of organic nitrogen (manure) in place of chemical nitrogen (fertilizer) on crop yield and soil nutrient balance were investigated. The experiment was started in 2006, and the data were collected in 2010-2014. Four treatments with four repeti-tions were designed in the study — including CK (no fertilizer), NPK (chemical fertilizer in maize at N 200 kg·hm-2, P2O590 kg·hm-2, K2O 120 kg·hm-2; and in soybean at N 22.5 kg·hm-2, P2O560 kg·hm–2, K2O 67.5 kg·hm-2), C7M3 (the total amounts of N, P and K were same as NPK treatment, in which 70% N was from chemical fertilizer and 30% N from organic cattle manure), and then C4M6 (60% N was from organic cattle manure and 40% N from chemical fertilizer, the amounts of P and K were the same as the treatment NPK). The results showed that: 1) compared with CK, treatments of NPK, C7M3 and C4M6 all increased soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP) and available potassium (AK). Furthermore, SOM content in C4M6 was significantly higher than that in NPK (P < 0.05). The contents of TN, AP and AK increased with increasing organic manure sup-plement. 2) The yields of maize and soybean in the fertilizer treatments were respectively 4.15-4.36 and 2.47-2.58 times higher than that in CK. Crop yield order in fertilizer treatments was C4M6 > NPK > C7M3, but there was no significant difference among treat-ments (P> 0.05). 3) For CK treatment, maize yield decreased by 5.45 g·m-2·a-1, while soybean yield increased by 1.50 g·m-2·a-1 during experimental period. The yields of both maize and soybean increased under long-term fertilization as the experiment went on. 4) In the experiment, K deficit was observed in organic manure treatments and CK during maize growth period, but N deficit ap-peared in all treatments during soybean growth period. In the maize-soybean relay intercropping system, K deficit of 7.9 kg·hm-2·a-1 was observed only in C4M6. P surplus was observed for all fertilizer treatments with surplus amounts of 81.2 kg(P)·hm-2, 83.4 kg(P)·hm-2 and 74.8 kg(P)·hm-2 in NPK, C7M3 and C4M6 treatments, respectively. In summary, based on the characteristics of nutrient balance and crop yield, that partial replacement of chemical nitrogen fertilizer by cattle manure was reasonable. We recommend that farmers should "reduce N, maintain P and increase K" during maize growth period, but should "maintain N and reduce P and K" in soybean growth period in maize-soybean agricultural ecosystem in karst peak-cluster depression areas.